Cast alloy for valve seat-insert

ABSTRACT

This invention relates to a cast alloy for valve seat-insert having an excellent wear resistance for use in an automobile engine consuming lead-free gasoline. The present invention relates to a cast alloy for valve seat-insert comprising fundamentally in weight ratio 0.80 to 2.50 % of C, 0.20 to 3.0 % of Si, 0.10 to 5.0 % of Mn, 0.03 to 0.50 % of P, 0.02 to 0.30 % of S, 13.0 to 28.0 % of Ni, 10.0 to 30.0 % of Cr, 0.1 to 5.0 % of Mo, 0.02 to 0.20 % of N, and the remaining part consisting of iron and a slight amount of impurities.

United States Patent [191 Kusaka et a1. 1 1

CAST ALLOY FOR VALVE SEAT-INSERT Assignees: Honda R & D Co., Ltd., Wako-City; Tokushu Seiko Co., Ltd., Kawasaki-City, both of, Japan Filed: Nov. 2, 1972 Appl. No.: 303,026

Foreign Application Priority Data May 17,1972 Japan 47-48124 US. Cl. 75/128 A, 75/128 C, 75/128 D, 75/128 N, 75/128 P, 75/128 W Int. CL. C22c 39/20, C22c 39/26, C22c 39/36, C22c 39/44, C22c 39/50, C22c 39/54 Field of Search; 75/128 W, 128 A, 128 C,

75/128 D, 128 N, 128 P, 122

References Cited UNITED STATES PATENTS 12/1942 Krivobok. 75/128 W 1 Jan. 7, 1975 3,152,934 10/1962 Lula 7 5/128 W 3,198,631 8/1965 Jones 75/128 W 3,235,417 2/1966 Roy 75/128 W 3,573,034 3/1971 Denhard 75/128 W 3,758,294 9/1973 Bellot 75/128 W Primary Examiner--C. Lovell Assistant Examiner-Arthuri. Steiner Attorney, Agent, or Firm-George B. Oujevolk 57 ABSTRACT This invention relates to a cast alloy for valve seatinsert having an excellent wear resistance for use in an automobile engine consuming lead-free gasoline. The present invention relates to a cast alloy for valve seatinsert comprising fundamentally in weight ratio 0.80 to 2.50 of C, 0.20 to 3.0 ofSi, 0.10 to 5.0 of Mn, 0.03 to 0.50 of P, 0.02 to 0.30 72 of S, 13.0 to 28.0 of Ni, 10.0 to 30.0 of Cr, 0.1 to'5.0 of Mo, 0.02 to 0.20 of N, and. the remaining part consisting of iron and a slight amount of impurities.

1 Claim, No Drawings CAST ALLOY FOR VALVE SEAT-INSERT BACKGROUND OF THE INVENTION This invention relates to a cast alloy for valve seatinsert having an excellent wear resistance for use in an automobile engine consuming lead-free gasoline. The cast alloy according to the present invention is a phosphorus-containing precipitation-hardening type austenite alloy which can reach the ordinary temperature hardness of more than H C 40 carrying out an aging treatment after a solution treatment. Accordingly, the cast alloy according to the present invention has such features that it exhibits an excellent creep resistance at a high temperature and an improved corrosion resistance, and it is particularly excellent in the wear resistance when used as a valve seat insert for automobile engine.

SUMMARY OF THE INVENTION The present invention has disclosed that the above mentioned excellent properties are obtained in a phosphorous-containing precipitation-hardening type austenite alloy having the following limited chemical composition; (1) C: 0.80 2.50 (2) Si: 0.20 3.0 (3) Mn: 0.10 5.0 (4) P: 0.03 0.50 (5) S: 0.02 0.3 (6) Ni: 13.0 28.0 (7) Cr: 10.0 30.0 (8) M: 0.1 5.0 (9) N: 0.02 0.20 the above percentages being all by weight, and the remaining part consists of iron and a slight amount of impurities.

The valve seat-insert is a part which plays an important role of maintaining an air-tightness in the cylinder by hitting and slide-contacting the suction valve and the exhaust valve at high temperatures. Gasoline presently used contains lead for the purpose of raising its octane-value. However, when lead burns in the cylinder, it is converted in lead oxide, and a part of said lead adheres to the exhaust valve and the valve seat-insert to play a role of a lubricant.

Heretofore, 1 C 8 Cr steel, 1.5 C l3 Cr steel or the like has been used as a valve seat alloy for use in the automobile engine. However, in the case of using lead-free gasoline, since lead oxide acting as a lubricant is not produced as a combustion product, the coefficient of friction between the exhaust valve and the valve seat becomes large, and it has been experienced that the instantaneous deposition phenomenon due to the metallic contact between the valve and the valve seat produces an abnormal wear of the valve seat. Particularly, in the case of using an exhaust valve in which a stellite filling has been applied onto the face of the valve, the wear of the valve seat is remarkable.

DETAILED DESCRIPTION OF THE INVENTION As a result of exhaustive studies, the present inventors have succeeded in obtaining an alloy having an excellent wear resistance as avalve seat-insert for an automobile engine using lead-free gasoline by adding further phosphorus to a high-carbon Cr Ni austenite alloy in which the matrix has been enhanced by adding Mo and N thereto thereby to impart a precipitation hardening property to the alloy, and further remarkably improve the wear resistance. This alloy has the following chemical composition;

Substance Percentage Substance Percentage Carbon 0.80 2.50 Nickel 13.0 28.0 Silicon 0.20 3.0 Chromium 10.0 30.0 Manganese 0.10 5.0 Molybde- 0.1 5.0

num Phosphorus 0.03 0.50 Nitrogen 0.02 0.20 Sulphur 0.02 0.30

In the alloy according to the present invention C is bonded to Cr to form a hard carbide and raise the wear resistance, and is solidsoluble in the austenite to increase the strength. However, C is added at less than 0.80 the wear resistance is inferior and at more than 2.5 the tenacity is lowered. Therefore C was selected to be in a range of from 0.80 to 2.5

Si improves acid-proof and castability of the alloy. When Si is added to the alloy less than 0.2 the fluidity of the molten bath is inferior. When Si is added more than 3 the tenacity of the alloy decreases. Accordingly, Si was selected to be in a range of from 0.2 to 3.0

Mn is added as a deoxidant. Since it has an effect of enhancing austenite, the amount of Mn to be added was selected to be 0.10 to 5.0

P is necessary for imparting a precipitationhardening property to the alloy. However, it has little effect when it is added at less than 0.03 and when it is added at more than 0.50 its tenacity decreases. Therefore, it was selected to be in a range of from 0.03 to 0.50

S is effective in improving the fitness of the valve to the valve seat. It is added to the alloy to improve its machinability in the high hardness after aging. However, at less than 0.02 its effect is small and at more than 0.30 its tenacity decreases. Therefore, it was selected to be in a range of from 0.02 to 0.30

Ni is effective in converting the structure into austenite, improving the wear resistance, increasing the strength at the ordinary temperature and that at the high temperature, and maintaining the tenacity. It acts to improve fitness to the valve face. At less than 13 its effect is small, and at more than 28 the improvement of its effect is also small. It is, therefore, selected to be in a range of from 13.0 to 28.0

Cr is effective in forming a film on the surface of alloy, improving the antioxidation property and the wear resistance. In the case of Cr being less than 10.0 it is insufficient in antioxidation property, wear resistance and strength. When it is added more than 30 the te nacity of alloy is deteriorated and its machinability is also decreased, and therefore, it was selected to be in a range of from 10.0 to 30.0

M0 is effective in increasing the strength at the high temperature, enhancing the matrix and improving the wear resistance. However, in an amount of less than 0.1 its effect is small and even if it is more than 5 the improvement of the effect is small and the price of the alloy becomes expensive, and therefore, it was selected to be in a range of from 0.1 to 5.0

N is solid-soluble in austenite, and effective in increasing the hardness, increasing the strength at the high temperature, and improving the wear resistance. It is also effective in improving fitness. However, in the case where it is used at less than 0.02 its effect is small, and when it is more than 0.20 the tenacity as well as the castability of the alloy is decreased. it was, therefore, limited to 0.02 to 0.20

W forms a hard carbide and the structureis pulverized, and is effective in improving the wear resistance. At less than 0.1 its effect is small and even when it is added to the alloy at more than 5 the improvement in the effect is small. It was, therefore, selected to be in a range of from 0.1 to 5.0

V is also effective in forming a hard carbide, and pulverizing the structure and improving the wear resistance. At less than 0.1 its effect is small, and at more than 4 the'improvement of the effect is less, so that it was selected to be in a range of from 0.1 to 4.0

-Co is effective in enhancing the matrix, increasing the high temperature hardness, improving the fitness and reducing the wear of the valve seat. When Co is added at less than 0.5 its effect is small and even if it is added more than the improvement of the effect is small. It was, therefore, selected to be in a range of from 0.5 to 10.0 v

The functions of the alloy according to the present invention will be described hereinbelow with reference to the experimental results. Table 1 indicates the chemical compositions of respective samples.

(Table 1 (Table 3) Alloy No. Mean wear length t/hr) mutant-13 According to the results shown in Table 3 it has been proved that the alloys B, C, D, E and F according to the present invention are remarkably small in the mean wear amount of the valve seat and have respectively excellent functions on valve seats for lead-free gasoline.

As has been described in the foregoing, since in the alloy according to the present invention the castings are subjected to aging treatment at 700 C for 2 hours after it has been subjected to the solution treatment at 1,l00 C, the hardness is raised to approximately H C 41, its wear resistance, its antioxidation property and its corrosion proof are very excellent, and it has good fitness to the valve face, and it has very excellent func- Chemical composition of alloys tested Alloy Chemical composition No. C Si Mn P S Ni Cr N Mo V W Co A 1.20 0.40 0.65 0.01 0.05 8.9 B 1.91 1.41 1.19 0.21 0.14 20.5 23.2 0.10 2.4 C 1.90 1.38 1.10 0.21 0.16 20.4 23.6 0.11 2.4 1.62 D 1.92 1.39 1.11 0.20 0.15 20.3 23.2 0.10 2.5 6.3 E 1.91 1.40 1.05 0.21 0.14 20.3 23.3 0.11 2.6 1.46 5 8 F 1.93 1.41 1.07 0.21 0.14 20.4 23.4 0.11 2.5 2.4

(Table 2) Aged hardness Alloy No. Heat treatment Rockwell C hardness A 950C oil quenched 600C X 1hr Air cool 37.0 B 1 100C oil quenched, 700C 2hrs Air cool 41.0 C do. do. 41.0 D do. do. 41.2 E do. do. 41.6 F do. do. 41.0

tions when used as a valve seat for an automobile engine using lead-free gasoline.

What we claim is:

1. An alloy for use in a valve seat consisting, in weight ratio, essentially of 0.80 to 2.50 of C, 0.20 to 3.0

5 of Si, 0.10 to 5.0 of Mn, 0.03 to 0.50 of P, 0.02

to 0.30 of S, 13.0 to 28.0 of Ni, 10.0 to 30.0 of Cr, 0.1 to 5.0 of Mo, 0.02 to 0.20 of N and the balance iron. 

1. AN ALLOY FOR USE IN A VALVE SEAT CONSISTING, IN WEIGHT RATIO, ESSENTIALLY OF 0.80 TO 2.50% OF C, 0.20 TO 3.0% OF SI, O.10 TO 5.0% OF MN, 0.03 TO 0.50% OF P, 0.02 TO 0.30% OF S, 13.0 TO 28.0% OF NI, 10.0 TO 30.0% OF CR, 0.1 TO 5.0% OF MO, 0.02 TO 0.20% OF N AND THE BALANCE IRON. 